int test_for(int n, int m)
{
    for(int i = 0; i < n; ++i) {
        for(int j = 0; j < m; j++) {
            if(j % 3 == 0)
                continue;
            else if(j % 7 == 0)
                break;
        }
    }
}

int foo(void); // 声明

int test_swtch(int n, int m, int x)
{
    switch(m) {
        case 1:
        case 2:
            foo();
            break;
        case 3:
            m = m + n;
            break;
        default:
            n = m - n;
        case 4:
            switch(n) {
                case 5:
                    n++;
                    break;
                case 6:
                    n--;
            }
            m = m * n;
            break;
    }

    foo();
}



